Radiation-curable resin composition for adhesives

ABSTRACT

A radiation-curable resin composition for adhesives comprising (A) a bisphenol-type epoxy (meth)acrylate having a hydroxyl group, (B) a polyfunctional (meth)acrylate having an aliphatic cyclic structure or an aromatic cyclic structure other than the component (A), and (C) a photoinitiator, wherein the content of the component (A) and the content of the component (B) in the composition are respectively 30 wt % or more. The radiation-curable resin composition for adhesives of the present invention exhibits excellent adhesion to silver, silicon compound, and aluminum, superior moisture-heat resistance, and fast curability, especially at the edge of the disk, and therefore is very useful in the manufacture of optical disks in comparison with conventional adhesives.

The invention relates to a radiation-curable resin composition foradhesives comprising (A) a bisphenol-type epoxy (meth)acrylate having ahydroxyl group, (B) a polyfunctional (meth)acrylate having an aliphaticcyclic structure or an aromatic cyclic structure other than thecomponent (A), and (C) a photoinitiator. The invention also relates toan adhesive for optical disks comprising the composition, and to opticaldisks comprising the composition and/or the adhesive.

Recent progress in information technology represented by computerhardware technology, computer software technology, and communicationtechnology has enabled much more information to be transmitted at highspeed. Accompanied by this, recording media capable of recording moreinformation at high density have been demanded, and development of suchrecording media has progressed. As such high-density recording media, aDVD (digital video disc or digital versatile disk) has been developed asa general-purpose recording medium for the next generation. The DVD ismanufactured by attaching two disks together. Therefore, an adhesive forcausing two disks to adhere is necessary. Use of a hot-melt adhesive,heat-curable adhesive, anaerobic curable adhesive, and the like has beenattempted. However, the hot-melt adhesive has insufficient heatstability and weatherability and therefore softens at high temperature,thereby causing the disks to be separated or deformed due to a decreasein adhesion. Moreover, it is difficult to apply a hot-melt adhesive tothe two-layered DVD having a translucent film as a recording film due toinsufficient transparency. A problem with the heat-curable adhesive isits exothermic properties that cause substrates forming the disks to bedeformed due to heat during curing. Moreover, a long period of time isrequired for curing the adhesive. The anaerobic curable adhesiveexhibits inferior productivity because a long period of time is requiredfor curing the adhesive. In order to solve these problems, photocurableadhesives have been proposed. For example, Japanese Patent ApplicationsLaid-open No. 61-142545 and No. 6-89462 disclose UV-curable resinadhesives containing a urethane acrylate as a main component.

Silver, an alloy containing silver as a main component, silicon and analloy containing silicon as the main component are inexpensive incomparison with gold and are used as a material for a translucent filmfor DVD-9. However, in the case of replacing gold with silver, an alloycontaining silver as a main component, silicon, or a compound containingsilicon as a main component, sufficient adhesion may not be obtained dueto changes in adhesion with the adhesive. Moreover, silver, an alloycontaining silver as a main component, silicon, or a compound containingsilicon as a main component are chemically unstable in comparison withgold. As a result, in the case of using a conventional adhesive forDVDs, silver, an alloy containing silver as a main component, silicon,or a compound containing silicon as a main component is changed into ablack substance or a white substance when allowed to stand at a hightemperature and a high humidity for a long period of time, whereby dataon the DVD may not be readable due to a decrease in reflectance.

In addition, curability at the edge of the disk is also required.

A conventional UV-curable resin adhesive is not fully satisfactory withrespect to moisture-heat resistance, curability at the edge of the diskas well as adhesion to a translucent film made of silver, an alloycontaining silver as a main component, silicon or a compound containingsilicon as a main component or adhesion to a reflection film made ofaluminum, at the same time.

Accordingly, an object of the present invention is to provide aradiation-curable resin composition for adhesives excelling in adhesionto silver, a compound or an alloy containing silver as a main component,silicon, or a compound or alloy containing silicon as a main component,and aluminum or a compound or alloy containing aluminum as a maincomponent and having superior moisture-heat resistance and curability atthe edge of the disk in comparison with a conventional composition, andalso to provide an adhesive for optical disks comprising thecomposition.

It has been found that the above object can be achieved by a specificradiation-curable resin composition for adhesives given below.

Specifically, the present invention provides a radiation-curable resincomposition for adhesives comprising (A) a bisphenol-type epoxy acrylatehaving a hydroxyl group, (B) a polyfunctional (meth)acrylate having analiphatic cyclic structure or an aromatic cyclic structure other thanthe component (A), and (C) a photoinitiator, wherein the content of thecomponent (A) and the content of the component (B) in the compositionare respectively 30 wt % or more.

As examples of the bisphenol-type epoxy (meth)acrylate having a hydroxylgroup of the component (A) used in the radiation-curable resincomposition for adhesives of the present invention, a bisphenol A-typeepoxy (meth)acrylate having a hydroxyl group and a bisphenol F-typeepoxy (meth)acrylate having a hydroxyl group can be given, with thosepossessing a bisphenol A structure (i.e., bisphenol A-type epoxy(meth)acrylate) being preferable. As examples of the bisphenol-typeepoxy (meth)acrylate, an adduct of bisphenol A diglycidyl ether(meth)acrylate and the like can be given.

The component (A) preferably contains 1.5-3 (meth)acryloyl groups in onemolecule. The number average molecular weight of the component (A) ispreferably from 400 to 3,000.

As commercially available epoxy acrylates, Epoxy Ester 3002M, 3002A,3000M, 3000A (manufactured by Kyoeisha Chemical Co., Ltd.), EA-1370(manufactured by Mitsubishi Chemical Corporation), Viscoat #540(manufactured by Osaka Organic Chemical Industry Ltd.), SP-1506,SP-1507, SP-1509, SP-1519-1, SP-1563, SP-2500, VR60, VR77, VR90(manufactured by Showa Highpolymer Co., Ltd.), and the like can begiven.

The proportion of the component (A) used in the radiation-curable resincomposition for adhesives of the present invention is usually 30 wt % ormore, preferably 35 wt % or more, and more preferably 40 wt % or more ofthe total amount of the composition. If the proportion of the component(A) is less than 30 wt %, it is difficult to maintain sufficientadhesion to metal layers of silver, a compound or an alloy containingsilver as a main component, silicon, or a compound or alloy containingsilicon as a main component, or aluminum or a compound or alloycontaining aluminum as a main component, and the like. When silver,silicon or aluminum are used in a compound or alloy, the preferably arepresent as the main component, i.e as the component having the highestweight percentage in the total composition forming the translucent orreflective layer.

In this text, the term polyfunctional (meth)acrylate is defined as a(meth)acrylate having more than one (meth)acrylate groups.

As polyfunctional (meth)acrylates possessing an aliphatic cyclicstructure or aromatic cyclic structure other than the component (A) thatcan be used in the present invention as the component (B),polyfunctional (meth)acrylates possessing an aliphatic cyclic structurehaving 6-12 carbon atoms or an aromatic cyclic structure having 6-12carbon atoms can be given. As the polyfunctional (meth)acrylatespossessing an aliphatic cyclic structure, C₂-C₄ alkylene oxide adductsof hydrogenated bisphenol A di(meth)acrylate and C₂-C₄ alkylene oxideadducts of bisphenol F di(meth)acrylate such as tricyclodecanemethanoldi(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, ethylene oxideadduct of hydrogenated bisphenol A di(meth)acrylate, ethylene oxideadduct of hydrogenated bisphenol F di(meth)acrylate, propylene oxideadduct of hydrogenated bisphenol A di(meth)acrylate, propylene oxideadduct of hydrogenated bisphenol F di(meth)acrylate, and the like can begiven. As the polyfunctional (meth)acrylates possessing an aromaticcyclic structure, C₂-C₄ alkylene oxide adducts of bisphenol Adi(meth)acrylate and C₂-C₄ alkylene oxide adducts of bisphenol Fdi(meth)acrylate such as ethylene oxide adduct of bisphenol Adi(meth)acrylate, ethylene oxide adduct of bisphenol F di(meth)acrylate,propylene oxide adduct of bisphenol A di(meth)acrylate, propylene oxideadduct of bisphenol F di(meth)acrylate, and the like can be given.

To increase the rigidity and strength of the adhesive, a polyfunctional(meth)acrylate possessing an aliphatic cyclic structure is preferablyused as the polyfunctional (meth)acrylate component (B). The use oftricyclodecanedimethanol di(meth)acrylate as the component (B) is evenmore preferable. It is also possible to use as component (B) a mixtureof polyfunctional (meth)acrylates possessing an aliphatic cyclicstructure or aromatic cyclic structure other than the component (A).However, preferably component (B) is not a mixture. If the crosslinkingdensity of the adhesive is too high, the cure shrinkage rate increasesand warping of the disk occurs. To prevent this problem, the component(B) preferably contains on average 1.5-3 (meth)acryloyl groups in onemolecule. Most preferably, component (B) contains 2-3 (meth)acryloylgroups in the molecule.

As examples of commercially available products suitably used as thecomponent (B), SA-1002, SA-2006, DX-TEMA (manufactured by MitsubishiChemical Corporation), Viscoat #3700, Viscoat #700 (manufactured byOsaka Organic Chemical Industry Co., Ltd.), KAYARAD R-551, R-71 2,R-604, R-684, HBA-024E, HBA-024P (manufactured by Nippon Kayaku Co.,Ltd.), ARONIX M-203, M-208, M-210 (manufactured by Toagosei Co., Ltd.),CD401, CD406, CD540, CD541, CD542, SR348, SR349, SR480, CD581, CD582,SR601, SR602, CD9038, SR9036 (manufactured by Sartomer Company),GX-8345, GX-8465, GX-8448D, GX-8449 (manufactured by Daiichi KogyoSeiyaku Co., Ltd.), LIGHT-ESTER BP-2EM, BP-4EM, BP-4PA, LIGHT-ACRYLATEDCP-A, LIGHT-ACRYLATE BP-134 (manufactured by Kyoeisha Chemical Co.,Ltd.), and the like can be given.

The proportion of the component (B) used in the radiation-curable resincomposition for adhesives of the present invention is usually 30 wt % ormore, preferably 35 wt % or more, and more preferably 40 wt % or more ofthe total amount of the composition. If the amount of the component (B)used is less than 30 wt %, the rigidity and strength of the adhesivedecreases.

The following compounds can be given as examples of photoinitiators:2,2-dimethoxy-1,2-diphenylethan-1-one,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxy-cyclohexyl phenylketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide,bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 3-methylacetophenone,2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde,fluorene, anthraquinone, triphenylamine, carbazole,3-methylacetophenone, benzophenone, 4-chlorobenzophenone,4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, benzoin ethylether, benzoin propyl ether, Michler's ketone, benzyl dimethyl ketal,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one,4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl) ketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one,2,4,6-trimethylbenzoylphenyl phosphinate,2,4,6-trimethylbenzoyidiphenylphosphine oxide,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide,methylbenzoyl formate, thioxanethone, diethylthioxanthone,2-isopropylthioxanthone, 2-chlorothioxanthone, andoligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]. Ofthese, 2,2-dimethoxy-1,2-diphenylethan-1-one,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenylketone, 2,4,6-trimethylbenzoyidiphenylphosphine oxide, andbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are preferred. In orderto improve curability of the edge surface, use of two types ofphotoinitiators selected from these compounds in combination ispreferable.

As examples of commercially available products of these compounds,IRGACURE 184, 261, 369, 500, 651, 819, 907, 1700, 1800, 1850,2959,Darocur 953, 1116, 1173, 1664, 2273, 4265 (manufactured by CibaSpecialty Chemicals Co., Ltd.), Lucirin TPO, LR8728, LR8893(manufactured by BASF), Ubecryl P36 (manufactured by UCB), VICURE55(manufactured by Akzo), ESACURE KIP100F, KIP150 (manufactured byLamberti), KAYACURE CTX, DETX, BP-100, BMS, 2-EAQ (manufactured byNippon Kayaku Co., Ltd.), and the like can be given. Of these, Irgacure184, 500, 651, 819, Darocur 1173, 4265, Lucirin TPO, LR8728, and LR8893are preferable.

In order to maintain corrosion resistance and surface edge curabilityand to ensure rigidity of the adhesive, the amount of the component (C)used in the radiation-curable resin composition for adhesives of thepresent invention is 0.01-15 wt %, preferably 0.05-10 wt %, and stillmore preferably 0.1-10 wt %. When only2,4,6-trimethylbenzoyldiphenylphosphine oxide orbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is used as thecomponent (C), the amount is preferably 0.1-1.5 wt % from the viewpointof moisture-heat resistance.

The radiation-curable resin composition for adhesives of the presentinvention may further comprise (D) a dialkylamino benzoate. By theaddition of the component (D), tackiness on the surface edge can bereduced, and the curability of the surface edge can be improved when thedisk is set and cured. As the component (D) used in the presentinvention, alkyl esters (methyl ester, ethyl ester, propyl ester, butylester, isoamyl ester, etc.) of dialkylaminobenzoic acid (alkyldialkylaminobenzoate) can be given. As alkyl groups in the dialkylaminogroup, alkyl groups having 1-6 carbon atoms are preferable. As the esterresidue, alkyl groups having 1-6 carbon atoms are preferable. Thedialkylamino group and carboxyl group of dialkylaminobenzoate preferablybond to the benzene ring at a p-position. Of these, ethylp-dimethylaminobenzoate is particularly preferable.

As examples of commercially available products used as the component(D), KAYACURE EPA, KAYACURE DMBI (manufactured by Nippon Kayaku Co.,Ltd.), and the like can be given.

The proportion of the dialkylaminobenzoic acid used as the component (D)of the present invention is preferably 0.05-5 wt %, more preferably0.1-3 wt %, and particularly preferably 0.2-1 wt % in view of edgecurability and moisture-heat resistance.

The radiation-curable resin composition for adhesives of the presentinvention may further comprise (E) an aromatic thiol compound. Theaddition of the component (E) improves moisture-heat resistance whenusing silver, an alloy containing silver as a main component, siliconcompound, or an alloy containing silicon as a main component. As thearomatic thiol compound, an aromatic heterocyclic compound containing amercapto group is preferable. As specific examples of such a compound,mercaptobenzoxazole, mercaptobenzothiazole,1-phenyl-5-mercapto-1H-tetrazole, and the like can be given. Ascommercially available products of the component (E), Nocceler M,Nocceler M-P, Nocrac MB, Nocrac MMB (manufactured by OuchishinkoChemical Industrial Co., Ltd.), Accel M, Antage MB (manufactured byKawaguchi Chemical Industry Co., Ltd.), Sanceler M, Sanceler M-G(manufactured by Sanshin Chemical Industry Co., Ltd.), Soxinol M,Sumilizer MB (manufactured by Sumitomo Chemical Co., Ltd.), and the likecan be given.

In view of moisture-heat resistance with silver and silicon, the contentof the component (E) in the composition is preferably 0.01-5 wt %, andstill more preferably 0.05-4 wt %.

A (meth)acrylate compound containing at least one (meth)acryloyl groupin the molecule other than the components (A) and (B) may be added tothe composition of the present invention. Any of monofunctionalcompounds containing one (meth)acryloyl group and polyfunctionalcompounds containing two or more (meth)acryloyl groups may be used.These compounds may be used in combination at an appropriate proportion.As the (meth)acrylate compound containing at least one (meth)acryloylgroup in the molecule other than the components (A) and (B),tetrafurfuryl acrylate, 4-hydroxybutyl acrylate, tetraethylene glycoldiacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate,and the like can be given.

The composition of the present invention may additionally contain aurethane (meth)acrylate. A urethane (meth)acrylate can be prepared byreacting a polyol compound, a polyisocyanate compound, and a hydroxylgroup-containing (meth)acrylate compound.

As the polyol compound, polyether polyols, polyester polyols,polycarbonate polyols, polycaprolactone polyols, aliphatic hydrocarbonshaving two or more hydroxyl groups in the molecule, alicyclichydrocarbons having two or more hydroxyl groups in the molecule,unsaturated hydrocarbons having two or more hydroxyl groups in themolecule, and the like can be used. These polyols may be used eitherindividually or in combination of two or more.

As examples of polyether polyols, aliphatic polyether polyols, alicyclicpolyether polyols, and aromatic polyether polyols can be given.

As a method for synthesizing the urethane (meth)acrylates, the followingmethods (i) to (iii) can be given. However, the method is not limited tothese.

-   -   (i) A method of reacting a polyisocyanate (b) and a hydroxyl        group-containing (meth)acrylate (c), and reacting the resulting        product with a polyol (a).    -   (ii) A method of reacting the polyol (a), polyisocyanate (b),        and hydroxyl group-containing (meth)acrylate (c) at the same        time.    -   (iii) A method of reacting the polyol (a) and polyisocyanate        (b), then reacting the resulting compound with the hydroxyl        group-containing (meth)acrylate (c).

It is preferable to synthesize the urethane (meth)acrylate used in thepresent invention using a urethanization catalyst such as coppernaphthenate, cobalt naphthenate, zinc naphthenate, di-n-butyltindilaurate, triethylamine, 1,4-diazabicyclo[2.2.2]octane, or1,4-diaza-2-methylbicyclo[2.2.2]octane in an amount of 0.01-1 part byweight for 100 parts by weight of the reaction product. The reactiontemperature is usually from 0 to 90° C., and preferably from 10 to 80°C.

Silane coupling agents other than the component (E) may be added to thecomposition of the present invention in addition to the components (A)to (E).

The composition of the present invention may additionally containradically polymerizable compounds other than the compounds containing anacryloyl group. N-vinylcaprolactam and the like can be giving asexamples of this compound.

Moreover, epoxy resins, polyamides, polyamideimides, polyurethanes,polybutadienes, chloroprenes, polyethers, polyesters, pentadienederivatives, SBS (styrene/butadiene/styrene block copolymer),hydrogenated SBS, SIS (styrene/isoprene/styrene block copolymer),petroleum resins, xylene resins, ketone resins, fluorine-containingoligomers, silicone oligomers, polysulfide oligomers, and the like maybe added to the composition of the present invention as other additives.

In addition to the above additives, paint additives such asantioxidants, UV absorbers, light stabilizers, aging preventives,anti-foaming agents, leveling agents, antistatic agents, surfactants,preservatives, heat-polymerization inhibitors, plasticizers, andwettability improvers may be added to the composition of the presentinvention. As examples of the antioxidants, Irganox 1035 (manufacturedby Ciba Specialty Chemicals Co., Ltd.) and the like can be given.

The viscosity of the composition of the present invention is preferably10-10,000 mPa.s, still more preferably 50-5,000 mPa.s, and particularlypreferably 150-2,000 mPa.s.

It is preferable to add each component so that the glass transitiontemperature of the resulting cured product is −30 to 250° C., preferably0 to 200° C., and even more preferably 50 to 180° C. If the glasstransition temperature is too low, the cured product softens in summeror in a closed sunny room at high temperature, whereby a substrate maybe dislodged or may move due to decreased adhesion. If the glasstransition temperature is too high, adhesion may be insufficient or thesubstrate may break when dropped or bent.

The term “glass transition temperature” used herein means a temperatureindicating a maximum value of the loss tangent (tan δ) measured using adynamic viscoelasticity measurement device at an oscillation frequencyof 10 Hz.

The composition of the present invention is cured by irradiating thecomposition with ultraviolet rays, visible rays, electron beams, or thelike in the same manner as in conventional photocurable resincompositions. The objects to be adhered can be easily adhered by placingthe composition of the present invention between them to produce anadhesive layer with a preferable thickness of 10-100 μm and curing thecomposition by irradiation using for example a metal halide lamp at adose preferably in the range of 50-2000 mJ/cm².

The photocured product of the composition of the present inventionpreferably has excellent transparency. For example, the cured productwith a thickness of 60 μm preferably has a light transmittance of 90% ormore at 600-700 nm. If the light transmittance is less than 90%, theappearance of an optical disk may be impaired. Moreover, light to readthe information stored in the disk is reduced by the adhesive layer ofthe cured product, thereby hindering read operations. Therefore, it ispreferable to prepare the composition of the present invention bycombining each component so that the light transmittance of the curedproduct is in the above range.

It is preferable to add each component so that the photocured product ofthe composition of the present invention has a refractive index of1.51-1.70 at 25° C. If the refractive index of the photocured product isout of this range, problems may occur when reading the informationstored in the disk.

The composition of the present invention exhibits good adhesion toplastics such as polycarbonate (PC) and polymethylmethacrylate (PMMA),metals such as gold, aluminum, and silver and alloys comprising at leastone of these metals, and to silicon, and compounds comprising silicon asthe main component, inorganic compounds such as glass, and the like.Therefore, the composition is suitable as an adhesive for optical disks.

EXAMPLES

The present invention will be described by examples, which should not beconstrued as limiting the present invention.

Synthesis of Urethane Acrylate:

Synthesis Example 1

A 1-liter separable flask equipped with a stirrer and a thermometer wascharged with 209 g of isophorone diisocyanate, 0.2 g of3,5-di-t-butyl-4-hydroxytoluene, and 0.8 g of di-n-butyltin dilaurate.The mixture was stirred and cooled to 10° C. in a water bath in dry air.109 g of 2-hydroxyethyl acrylate was added slowly at 10-35° C. over onehour and allowed to react. After the addition of 305.5 g ofpolytetramethylene glycol with an average molecular weight of 650 (“PTMG650” manufactured by Mitsubishi Chemical Corp.), the mixture was allowedto react at 40-60° C. for 5 hours while stirring. The reaction productwas removed to obtain urethane acrylate (UA) with a number averagemolecular weight of 1,300. This component is described in Tables 1 and 2as Oligomer (UA)

Examples and Comparative Examples

Preparation of Radiation-Curable Resin Composition for Adhesives

A reaction vessel equipped with a stirrer was charged with components ofthe compositions shown in Tables 1 and 2. The mixture was stirred for 1hour at 50° C. to prepare the coating film compositions of Examples 1-13and Comparative Examples 1-3. The components shown in Tables 1 and 2 areas follows. The amount of the components in Table 1 is indicated byparts by weight.

Component (A)

Bisphenol A diglycidyl ether acrylate adduct (“VR-77” manufactured byShowa Highpolymer Co., Ltd.)

Component (B)

Tricyclodecanedimethylol diacrylate (“Upimer SA-1 002” manufactured byMitsubishi Chemical Corp.)

Bisphenol A-type ethylene oxide addition diacrylate (“Viscoat #700”manufactured by Osaka Organic Chemical Industry Co., Ltd.)

Component (C)

2,2-Dimethoxy-1,2-diphenylethan-1-one (“Irgacure 651” manufactured byCiba Specialty Chemicals Co., Ltd.)

2-hydroxy-2-methyl-1-phenyl-propan-1-one (“Darocur 1173” manufactured byCiba Specialty Chemicals Co., Ltd.)

1-Hydroxycyclohexyl phenyl ketone (“Irgacure 184” manufactured by CibaSpecialty Chemicals Co., Ltd.)

2,4,6-Trimethylbenzoyidiphenylphosphine oxide (“Lucirin TPO-X”manufactured by BASF)

Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (“Irgacure 819”manufactured by Ciba Specialty Chemicals Co., Ltd.)

Component (D)

Ethyl dimethylaminobenzoate (“KAYACURE EPA” manufactured by NipponKayaku Co., Ltd.)

Component (E)

2-Mercaptobenzothiazole (manufactured by Tokyo Kasei Kogyo Co., Ltd.)

Other Components

Tetrafurfurylacrylate (“Viscoat 150” manufactured by Osaka OrganicChemical Industry Co., Ltd.)

Tetraethylene glycol diacrylate (“Light Acrylate 4EGA” manufactured byKyoeisha Chemical Co., Ltd.)

Tripropylene glycol diacrylate (“NK ESTER APG-200” manufactured byShin-Nakamura Chemical Co., Ltd.)

N-Vinylcaprolactam (manufactured by BASF)

2,2-thio-diethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate](“Irganox 1035” manufactured by Ciba Specialty Chemicals Co., Ltd.)

The compositions thus prepared (compositions of Examples 1-13 andComparative Examples 1-3) were applied to a substrate to form a curedfilm and the adhesion to substrates, moisture-heat resistance, and edgecurability were measured and evaluated as described below.

(1) Adhesion to Substrates (Adhesiveness)

The composition was applied onto a silver film, silicon film, oraluminum film deposited on a PC substrate using a sputtering method. Thecomposition was irradiated at a dose of 100 mJ/cm² in a nitrogenatmosphere to obtain a cured film of the composition with a thickness of50 μm. The cured film was then subjected to a cross cut cellophane tapepeeling test. A Crosscut Cellotape (trademark) peeling test was repeated10 times. Adhesiveness was judged as satisfactory when the adhesive didnot peel off the silver film, silicon film, or aluminum film,respectively. Those receiving satisfactory results 10 times were judgedas “Excellent”, those receiving satisfactory results 8-9 times werejudged as “Very good”, and those receiving satisfactory results 6-7times were judged as “Good”. If peeling was observed or more times,adhesiveness was judged as “Bad”.

(2) Moisture-Heat Resistance

Three pairs of PC substrates with a different coated film depositedthereon by sputtering; (1) a translucent silver film and a silver film,(2) a translucent silver film and an aluminum film, and (3) atranslucent silicon film and an aluminum film, were provided. A coatedfilm with a thickness of 50 μm was produced by spin coating between eachpair of PC substrates and irradiated at a dose of 500 mJ/cm² in the airto cause them to adhere. In the case where abnormalities such as foam orcorrosion were observed in the adhesive layer or the interface betweenthe adhesive and the substrates after allowing to stand in athermo-hygrostat at a temperature of 80° C. and a relative humidity of95% for 192 hours, moisture-heat resistance of the composition wasjudged as “Bad”. In the case where no abnormalities were observed,moisture-heat resistance of the composition was judged as “Good”. Thosenot displaying abnormalities after being allowed to stand in athermo-hygrostat at a temperature of 80° C. and a relative humidity of95% for 192 hours were judged as “Very good”, and those not displayingabnormalities after 384 hours were judged as “Excellent”.

(3) Edge Curability

Three pairs of PC substrates with a different coated film depositedthereon by sputtering; (1) a translucent silver film and a silver film,(2) a translucent silver film and an aluminum film, and (3) atranslucent silicon film and an aluminum film, were provided. A coatedfilm with a thickness of 50 μm was produced by spin coating between eachpair of PC substrates and irradiated at a dose of 500 mJ/cm² in the airto cause them to adhere. In the case where tackiness (viscosity) wasnoted when the edge of the disk thus obtained was touched, edgecurability of the composition was judged as “Bad”. In the case wherethere was no tackiness, edge curability of the composition was judged as“Good”. Furthermore, those not displaying tackiness when irradiated at adose of 200 mJ/cm² were judged as “Very good”, and those not displayingtackiness when irradiated at a dose of 100 mJ/cm² were judged as“Excellent”.

The results of the above evaluations are shown in Tables 1 and 2. As isclear from these results, the compositions in Examples 1-13 containingthe essential components (A) to (C) exhibited excellent curability,excellent moisture-heat resistance, and good adhesion to the sputteredmetal surface. The composition in Comparative Example 1 which containeda low content of the component (A) exhibited poor curability. Thecompositions in Comparative Examples 2 and 3 which contained a lowcontent of the component (B) exhibited inferior moisture-heat resistanceand inferior edge-curability. TABLE 1 Example 1 Example 2 Example 3Example 4 Example 5 Example 6 Example 7 Example 8 A VR77 (bisphenol Adiglycidyl ether acrylate 40 35 30 30 35 35 35 35 adduct) BTricyclodecanedimethanol diacrylate 40 40 30 30 58.2 58.2 58.7 Ethyleneoxide addition bisphenol A diacrylate 30 Tetrafurfuryl Acrylate 5Tetraethylene glycol diacrylate 7.7 7.7 11.7 14.7 17.7 Tripropyleneglycol diacrylate 5 16 13 N-Vinyl caprolactam 5 5 5 5 5 Oligomer (UA) C2,2-Dimethoxy-1,2-diphenylethan-1-one 3 3 3 3 3 3 3 32-Hydroxy-2-methyl-1-phenylpropan-1-one 3 3 3 3 3 3 3 31-Hydroxycyclohexyl phenyl ketone2,4,6-Trimethylbenzoyldiphenylphosphine oxideBis(2,4,6-trimethylbenzoyl)phenylphosphine oxide D Ethyldimethylaminobenzoate 0.5 0.5 0.5 0.5 0.5 0.5 E 2-Mercaptobenzothiazole0.5 0.5 0.5 0.5 0.5 0.5 Irganox 1035 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3Adhesiveness Translucent silver film Excellent Very good Good Good Verygood Very good Very good Very good Silver film Excellent Very good GoodGood Very good Very good Very good Very good Aluminum film ExcellentVerygood Good Good Very good Very good Very good Very good Translucentsilicon film Excellent Very good Good Good Good Good Good GoodCombination of translucent silver film and silver film Moisture-heatresistance Excellent Excellent Very good very good Very good ExcellentVery Good Good Edge curability Excellent Excellent Excellent ExcellentVery good Good Good Excellent Combination of translucent silver film andaluminum film Moisture-heat resistance Excellent very good Very goodVery good Very good Very good Very good Good Edge curability ExcellentExcellent Excellent Excellent Very good Good Good Excellent Combinationof translucent silicon film and aluminum film Moisture-heat resistanceVery good Very good Good Good Good Very good Good Good Edge curabilityExcellent Excellent Excellent Excellent Very good Good Good Excellent

TABLE 2 Com- Com- Com- Example Example Example Example parative parativeparative Example 9 10 11 12 13 Example 1 Example 2 Example 3 A VR77(bisphenol A diglycidyl ether acrylate 35 35 35 35 35 10 40 35 adduct) BTricyclodecane dimethanol diacrylate 40 40 40 40 40 60 20 25 Ethyleneoxide addition bisphenol A Diacrylate Tetrafurfuryl Acrylate 4.2 4.7 10Tetraethylene glycol diacrylate 7.7 7.7 7.7 7.7 7.7 4 4 Tripropyleneglycol diacrylate 5 5 5 5 5 10 8.7 N-Vinyl caprolactam 5 5 5 5 5Oligomer (UA) 15 15 15 C 2,2-Dimethoxy-1,2-diphenylethan-1-one 3 3 3 3 33 3 3 2-Hydroxy-2-methyl-1-phenylpropan-1-one 1.5 1.5 3 3 31-Hydroxycyclohexyl phenyl ketone 3 2,4,6-Trimethylbenzoyldiphenylphosphine oxide 1.5 3 Bis(2,4,6-trimethylbenzoyl)phenylphosphine1.5 3 oxide D Ethyl dimethylaminobenzoate 0.5 0.5 0.5 0.5 0.5 0.5 E2-Mercaptobenzothiazole 0.5 0.5 0.5 0.5 0.5 Irganox 1035 0.3 0.3 0.3 0.30.3 0.3 0.3 0.3 Adhesiveness Translucent silver film Very good Very goodVery good Very good Very good Bad Very good Good Silver film Very goodVery good Very good Very good Very good Bad Very good Good Aluminum filmVery good Very good Very good Very good Very good Bad Very good Verygood Translucent silicon film Very good Very good Very good Very goodVery good Bad Very good Good Combination of translucent silver film andsilver film Moisture-heat resistance Excellent Excellent Excellent Verygood Very good Very good Bad Bad Edge curability Excellent ExcellentExcellent Excellent Excellent Very good Bad Bad Combination oftranslucent silver film and aluminum film Moisture-heat resistance Verygood Very good Very good Very good Very good Good Bad Bad Edgecurability Excellent Excellent Excellent Excellent Excellent Very goodBad Bad Combination of translucent silicon film and aluminum filmMoisture-heat resistance Very good Very good Very good Very good Verygood Good Bad Bad Edge curability Excellent Excellent ExcellentExcellent Excellent Very good Bad Bad

1. A radiation-curable resin composition for adhesives comprising (A) abisphenol-type epoxy (meth) acrylate having a hydroxyl group, (B) apolyfunctional (meth) acrylate having an aliphatic cyclic structure oran aromatic cyclic structure other than the component (A), and (C) aphotoinitiator, wherein the content of the component (A) and the contentof the component (B) in the composition are respectively 30 wt % ormore.
 2. The radiation-curable resin composition for adhesives accordingto claim 1, wherein the component (A) comprises a bisphenol A skeleton,has a number average molecular weight of 400-3000, and is contained inthe composition in an amount of 35 wt % or more.
 3. Theradiation-curable resin composition for adhesives according to claim 1,wherein the component (C) comprises two or more different compounds. 4.The radiation-curable resin composition for adhesives according to claim1, further comprising (D) a dialkylamino benzoate.
 5. Theradiation-curable resin composition for adhesives according to claim 1,further comprising (E) an aromatic thiol compound.
 6. Theradiation-curable resin composition for adhesives according to claim 5,wherein the content of the component (E) in the composition is 0.01-5 wt%.
 7. An adhesive for optical disks comprising the radiation-curableresin composition according to claim
 1. 8. An optical disk comprisingthe radiation curable resin composition according to claim
 1. 9. Anoptical disk comprising the adhesive according to claim
 7. 10. Anoptical disk comprising a translucent film made of silver or a compoundor an alloy comprising silver as the main component, a reflection filmmade of aluminum or a compound or alloy containing aluminum as the maincomponent and a suitably cured adhesive according to claim
 7. 11. Anoptical disk comprising a translucent film made of silicon or a compoundor alloy comprising silicon as the main component, a reflection filmmade of aluminum or a compound or alloy containing aluminum as the maincomponent and a suitably cured adhesive according to claim
 7. 12. Theradiation-curable resin composition for adhesives according to claim 2,wherein the component (C) comprises two or more different compounds.